Field
The present disclosure relates generally to communication systems, and more particularly, to signal modulation and phase-shift-keying (PSK) pilot signals.
Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
OFDM signals may have a relatively high peak-to-average power ratio (PAPR). High PAPR may lead to the necessity of high-resolution analog-to-digital converters (ADCs), high-resolution digital-to-analog converters (DACs), and power amplifiers having high linearity. Oftentimes, high-linearity power amplifiers have lower power efficiency, due to the amount of power needed to produce an effective signal, as well as higher cost. Although OFDM may be commonly used in downlink transmissions from a base station, such as an evolved Node B (eNB), the disadvantages of power and cost associated with OFDM can make OFDM poorly suited for mobile devices that need reduced power consumption in order to maintain a long battery life.
For reduced PAPR, SC-FDMA can be used. The reduced PAPR associated with SC-FDMA enables increased power efficiency when compared to OFDMA. The reduced PAPR makes SC-FDMA suitable for transmissions from a mobile device/user equipment (UE), such as an uplink transmission of a UE operating according to the LTE standard of telecommunication. Although SC-FDMA reduces PAPR when compared to conventional OFDMA, SC-FDMA still has a relatively large PAPR when a relatively large number of tones are allocated for the uplink transmission of the signal.
Much effort has been made to reduce signal PAPR of OFDM and SC-FDMA signals without significant success. With the advent of internet of things (IOT), there is a growing need for very low-power wireless communication devices to enable extended battery life. This in turn calls for modulation schemes with very low PAPR.